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The grounds and buildings of highly loaded historic sites are continually changing due to environmental and human interaction, ecological erosion, disposition, erasure and the various levels of human intervention. These factors dissolve both physical structures and the meaning embedded in them, to varying degrees. In loaded historic sites, such as Auschwitz-Birkenau, revitalizing the ruins to their original state trivializes the Holocaust. On the other hand, creating an architecture that does not directly engage with existing conditions shows the inability to translate history into an architectural narrative and achieve an awareness of the events that took place there. The challenge then, is to ? nd a place for architecture to operate within, and to activate the ruins of these fragile sites.

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Polyvinyl Chloride (PVC), a plastic polymer composed of ∼43% hydrocarbon by weight and ~57% chlorine has become extensively used in our daily lives. However, the disposal of waste PVC plastics presents serious problems. The increased awareness of these problems requires the development of a reliable technique to dispose of these wastes in a safe and environmentally benign way that is devoid of the formation/release of organo-chlorine compounds. Chemical degradation of PVC is a technology that transforms PVC waste into completely new chemical products that don't contain chlorine. Sub-critical water (SCW) treatment is one of the most reliable technologies since SCW as a chemical reaction medium having adjustable physico-chemical properties. Hydrodechlorination (HDC), a reaction that replaces organically bound chlorine by hydrogen, can be accelerated by the presence of metal oxide catalysts (alumina supported palladium, Pd0/Al2O3) or raney nickel. When combined with SCW treatment, HDC offers a disposal process that is free from unwanted by-products. The rate of borohydride decomposition is accelerated by raney nickel. The HDC efficiency of virgin and formulated PVC in SCW under various reaction conditions of time and temperature was evaluated systematically. The time of reaction was varied from 1 to 4.5 hours and the temperature was varied from 150 to 280°C in the presence of palladium on alumina (Pd/Al2O3) or raney nickel. The efficiency of HDC varied from ~3% up to a completed dechlorination. Thus, organically bound chlorine in PVC in a water phase can be converted, virtually quantitatively, to chloride ion. / Response surface methodology (RSM) was used for experimental design and data analysis. The computer output from the Design-Expert software was used to optimize a model for the dechlorination as a function of time and temperature. A subsequent analysis of variance associated with the fitted model indicated a good fit between observed and predicted HDC efficiencies.

An in-depth study of the biodeterioration of the Hulett Aluminium hot roll mill emulsion, Prosol, was conducted. Samples of the emulsion in use at the hot roll mill were taken from various areas of the emulsion reticulation system in order to identify regions of highest microbial contamination. Standard plate count techniques and diagnostic procedures were employed to quantify and identify the microorganisms in these samples. In some of the highly contaminated areas of the emulsion reticulation system, microorganisms exceeded lxlO'CFUml'1 emulsion. A range of bacteria was identified which included members of the genera: Bacillus; Pseudomonas; Escherichia; Enterobacter; Sporosarcina; Micrococcus; Aeromonas; Chromobacterium and Desulfovibrio. Various fungi, including several yeasts, were also isolated and some of the filamentous spore-forming types were identified zsAspergillus spp.; Penicillium spp. and a Cladosporium sp. A visual scale was developed to assess the growth rate of the isolated microorganisms on a range of specific media containing various emulsion components as carbon and energy source. Although the results obtained by using this scale were not conclusive, a few biodegradable components were nonetheless identified. It was found that mixed cultures of the above microorganisms had a greater biodeteriorative effect on the emulsion than did any of the pure cultures when applied separately. This suggested complex microbial interactions were involved in the breakdown of the emulsion. A laboratory-scale model system representative of the Hulett Aluminium hot roll mill was designed and constructed to carry out a series of tests on unprotected and biocide-treated emulsions. A range of biocide concentrations were tested from which the minimum biocide inhibitory concentration was calculated. It was shown that microorganisms exposed to sublethal doses of the biocide Busan (active component glutaraldehyde) over a prolonged period of time, exhibited greater levels of tolerance and resistance to the biocide than did those microorganisms not previously exposed. It was deduced that less frequent, shock doses of biocide are more effective in the control and eradication of emulsion degrading microorganisms than are frequent, low level doses of the same biocide. In addition to the biocide studies, three imported so-called 'biostable' emulsions were evaluated as possible replacements for the susceptible Prosol. Of these three imported emulsions, two viz. HRF3 and Houghton Biostable were shown to be more resistant than Prosol to biodeterioration. After assessing the current hot roll mill management practices, a number of recommendations were made, including: the improvement of plant hygiene; education of the mill workers; improvement of emulsion monitoring; improvement of down-time management and improvement of biocide dosing regimes. Recommendations are also made for minimizing potential microbial growth in the new hot roll mill currently under construction at the Hulett Aluminium processing plant at Pietermaritzburg, South Africa. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

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